This invention relates generally to video game or video simulator controllers and more particularly to actuation mechanisms within joystick controllers.
Joystick controllers are used as an input device to computers running a video game/simulator software to control the directionality of a simulated system, such as an aircraft. The joystick requires two dimensional range of motion, i.e., both X and Y axes, to provide maximum directional control. In a personal computer running aircraft simulator software, for example, movement of the joystick along the X axis of the joystick changes the horizontal direction of the aircraft, while movement of the joystick along the Y axis of the joystick controls the vertical direction of the aircraft.
The position of the joystick may assume a multiplicity of unique coordinates, the exact number of unique coordinates being limited only by the resolution of the position sensors or transducers within the controller. Moreover, the user can swing the joystick between any of these positions in a sudden and unpredictable manner in response to a sudden change in the simulation conditions. This dynamic behavior of the joystick is used by the simulator to respond to the changed conditions.
In contrast, a throttle controller, for example, requires only one dimensional range of motion. The throttle controller is positionable along a single axis. The static position of the throttle controller along the axis determines the fuel setting input to an aircraft simulator. Typically, the throttle setting is set at a predetermined level and remains there for a given period of time. Although this level can be changed from time to time, e.g., take-off and landing, the rate and frequency of the change is substantially less than that of a joystick.
There are two primary means for detecting the joystick position. The first is an optical technique, the second is a mechanical technique. The present invention is an improved mechanical technique, thus, the optical technique is not discussed herein. The prior art mechanical technique uses two orthogonally-positioned potentiometers to detect the joystick position in two dimensions. Each potentiometer is dedicated to a particular joystick axis. Essentially, the translational movement of the joystick along an axis turns the stem of the corresponding potentiometer dedicated to that axis. The potentiometer setting is thus directly proportional to the coordinate of the joystick along the corresponding axis.
In prior art joysticks, the coupling between the joystick and the potentiometer stem is a direct drive connection. In the direct drive coupled joysticks, the potentiometer stem is directly connected to a corresponding gimbal. The stem of the potentiometer thus acts as the pivot point for the corresponding gimbal. Each gimbal rotates in one direction about the axis of the potentiometer stem and is resiliently held in a center of neutral position by a pair of springs mounted at opposite ends of the gimbal. As the gimbal is rotated by moving the joystick in one dimension it turns the corresponding potentiometer stem.
The direct drive connection subjects the potentiometer to a lateral force that lowers the reliability of the potentiometer. In using the joystick, a user commonly applies a downward force on the handle, especially in simulation programs that require sudden forceful movements of the joystick handle, such as in air combat flight simulators. In the direct drive joysticks, the downward force is applied directly to the stem of the potentiometer as a lateral force. This lateral force eventually causes the potentiometer to fail. Examples of direct connection joysticks, such as those described above, are found in some of the joystick products by Thrustmaster, Inc., of Tigard, Oreg., and CH, Inc., Vista, Calif.
The springs used to return the gimbal to the neutral position also exert a lateral force on the potentiometer stem that further lowers the reliability of the potentiometer. Each gimbal has two springs mounted thereon at opposite ends. Each spring has a center coil section, and two end portions. Each end portion has an orthogonal finger at the distal end thereof extending away from the coil portion. In the relaxed state the two fingers are spaced apart and substantially collinear.
In use, the coil of one of the springs is mounted on the potentiometer stem. One finger is connected to the gimbal and the other is connected to a mounting bracket holding the potentiometer. As the gimbal rotates so that the end portions cross, a force is generated that attempts to push the coil portion away from the end portions. This force is coupled to the potentiometer stem, as a lateral force, because the coil is mounted on the stem. A force in the opposite lateral direction is generated on the stem if the gimbal rotates in the opposite direction so that the end portions of the spring move away from each other. In addition to creating this lateral force, rotating the spring in this direction tends to permanently deform the spring because the spring is being expanded rather than compressed. To counteract this deformation, the second identical spring is used on the opposite side of the gimbal. The second spring is rotated by 180 degrees so that the second spring is compressed when the first spring is expanded and vice versa.
Accordingly, a need remains for an actuation and transducer mechanism for a joystick that is operable in two dimensions without exerting a lateral force on the potentiometer stem.